The present invention relates to printing devices. More particularly, the present invention relates to an apparatus and method for drying printing composition on a print medium.
Printing devices, such as ink jet printers and laser printers, use printing composition (e.g., ink or toner) to print images (text, graphics, etc.) onto a print medium in a printzone of the printing device. Inkjet printers may use print cartridges, also known as xe2x80x9cpensxe2x80x9d, which shoot drops of printing composition, referred to generally herein as xe2x80x9cinkxe2x80x9d, onto a print medium such as paper, transparency or cloth. Each pen has a printhead that includes a plurality of nozzles. Each nozzle has an orifice through which the drops are ejected. To print an image, the printhead is propelled back and forth across the page by, for example, a carriage while ejecting drops of ink in a desired pattern as the printhead moves. The particular ink ejection mechanism within the printhead may take on a variety of different forms known to those skilled in the art, such as thermal printhead technology. For thermal printheads, the ink may be a liquid, with dissolved colorants or pigments dispersed in a solvent.
In a current thermal system, a barrier layer containing ink channels and vaporization chambers is located between an orifice plate and a substrate layer. This substrate layer typically contains linear arrays of heating elements, such as resistors, which are energized to heat ink within the vaporization chambers. Upon heating, the ink in the vaporization chamber turns into a gaseous state and forces or ejects an ink drop from a orifice associated with the energized resistor. By selectively energizing the resistors as the printhead moves across the print medium, the ink is expelled in a pattern onto the print medium to form a desired image (e.g., picture, chart or text).
In order for the image to be fixed to the print medium so that it will not smear, the printing composition must be dried. The printing composition is dried by a combination of the solvent evaporating and the solvent absorbing into the print medium, both of which take time. Various factors control the amount of time required for a particular printing composition to dry. These factors include the type of print medium, the quantity of solvent in an printing composition, the amount of printing composition on the print medium, and ambient temperature and humidity. Ideally, the printing composition will be fixed to the print medium quickly to help prevent image smear, print medium cockle (print medium buckle toward a printhead), and print medium curl (curling along at least one edge of a print medium), as well as to help maximize printing device throughput.
To reduce the amount of this time, the surface of some types of print media may be specially coated to help speed drying. Other means may also be used such as special chemicals, generally know as xe2x80x9cfixersxe2x80x9d, that are applied to print media before or after printing.
Each of these above-described techniques have certain disadvantages. For example, specially coated print media may be relatively more expensive than uncoated print media. Fixers may become depleted during printing, resulting in no fixer being applied for the remainder of a print job, possibly causing some or all of the aforementioned problems, or the stopping of a print job to supply additional fixer, resulting in decreased printing device throughput and possible color hue shift on any print medium for which printing was halted.
An apparatus and method that decreased the amount of time required to dry or fix printing composition to a print medium while avoiding the above-described problems associated with other techniques would be a welcome improvement. Accordingly, the present invention is directed to drying printing composition on a print medium quickly to help prevent image smear, print media cockle, and print media curl. The present invention is also directed to helping maximize printing device throughput. The present invention is additionally directed to eliminating the need for specially coated media and fixers to accelerate drying.
Accordingly, an embodiment of a printing device in accordance with the present invention includes a printing mechanism for printing an image on a print medium and a metal belt for transporting the print medium. The printing device also includes an induction heater positioned adjacent the metal belt, the induction heater being configured to induce an alternating current in an area of the metal belt adjacent the induction heater, the alternating current uniformly heating the area of the metal belt adjacent the induction heater.
The above-described embodiment of a printing device in accordance with the present invention may be modified and include the following characteristics, as described below. The alternating current may be induced in the area of the metal belt adjacent the induction heater irrespective of movement of the metal belt. The printing mechanism may comprise an inkjet printhead.
An alternative embodiment of a printing device in accordance with the present invention includes structure for printing an image on a print medium and metallic structure for transporting the print medium. The printing device additionally includes structure for generating a varying magnetic flux through an area of the metallic structure for transporting that induces an alternating current in the area thereby uniformly heating the area.
The above-described alternative embodiment of a printing device in accordance with the present invention may be modified and include the following characteristics, as described below. The structure for printing may comprise an inkjet printhead. The metallic structure for transporting may comprise a metal belt. The structure for generating may comprise an induction heater positioned adjacent the metallic structure for transporting. The alternating current may be induced in the area of the metallic structure for transporting irrespective of movement of the metallic structure for transporting.
An embodiment of a method for use in a printing device, the printing device including a printing mechanism for printing an image on a print medium and a metal belt for transporting the print medium, includes generating a varying magnetic flux through an area of the metal belt. The method additionally includes inducing an alternating current in the area of the metal belt through which the varying magnetic flux passes and substantially uniformly heating the area of the metal belt through which the varying magnetic flux passes.
The above-described embodiment of a method in accordance with the present invention may be modified and include the following characteristics, as described below. A magnitude of the magnetic flux may be varied through the area of the metal belt. Alternatively or additionally, a direction of the magnetic flux may be varied through the area of the metal belt. The method may additionally include transferring heat from the area of the metal belt to the print medium to fix the image on the print medium. The alternating current may be induced in the area of the metal belt through which the varying magnetic flux passes irrespective of movement of the metal belt.
An embodiment of an inductive heating device in accordance with the present invention for use in a printing device, the printing device including a metal belt for transporting the print medium, includes a power source and a coil. The coil is coupled to the power source to produce a varying magnetic field around the coil and positioned adjacent the metal belt to induce an alternating current in an area of the metal belt throug which the varying magnetic field passes, the alternating current uniformly heating the area of the metal belt.
The above-described embodiment of an inductive heating device in accordance with the present invention may be modified and include the following characteristics, as described below. A magnitude of the magnetic field may vary. Alternatively or additionally, a direction of the magnetic field may vary. The alternating current may be induced in the area of the metal belt irrespective of movement of the metal belt.
With respect to each of the above-described embodiments, as well as others in accordance with the present invention, at least the following advantages are noted. The use of a metal belt or metallic structure for transporting is less expensive and complex to manufacture than a non-metal belt with electrical conductors, such as metallic wire loops, embedded or defined therein. Also, a metal belt or metallic structure for transporting is electrically conductive over its whole surface area, thereby providing more substantially uniform heating throughout than a non-metal belt with electrical conductors embedded or defined therein which tends to provide more localized heating in the areas adjacent the conductors. Additionally, induction heating in accordance with the present invention does not require movement of the metal belt or metallic means for transporting because a varying magnetic flux may be generated by changing an intensity and/or direction of a magnetic field through an area of the metal belt or metallic means for transporting. Furthermore, induction heating in accordance with the present invention does not require physical contact between the metal belt and the heating device, as with conductive heating designs, where substantially uniform physical contact is required between the metal belt and the heating device in order for heat transfer to occur. The requirement for such substantially uniform physical contact adds tolerance requirements to such conductive heating device designs. Elimination of the requirement of physical contact for heat transfer to occur and its associated tighter tolerances, helps reduce the complexity and cost of the present invention, as well as increase its operational efficiency.
The foregoing summary is not intended by the inventors to be an inclusive list of all the aspects, advantages, and features of the present invention, nor should any limitation on the scope of the invention be implied therefrom. This summary is provided in accordance with 37 C.F.R. Section 1.73 and M.P.E.P. Section 608.01(d). Additionally, it should be noted that the use of the word substantially in this document is used to account for things such as engineering and manufacturing tolerances, as well as variations not affecting performance of the present invention. Other objects, advantages, and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.